Also known as harvestmen, these harmless arachnids
are known for their exceptionally long walking legs, compared to
body size. They are not spiders.

These harmless arachnids are known for their exceptionally long walking legs, compared to body size. The difference between harvestmen and spiders is that in harvestmen the two main body sections (the abdomen with ten segments and cephalothorax, or prosoma and opisthosoma) are nearly joined, so that they appear to be one oval structure. In more advanced species, the first five abdominal segments are often fused into a dorsal shield called the scutum, which is normally fused with the carapace. Sometimes this shield is only present in males. The two most posterior abdominal segments can be reduced or separated in the middle on the surface to form two plates laying next to each other

The second pair of legs are longer than the others and works as antennae. This can be hard to see in short-legged species. They have a single pair of eyes in the middle of their heads, oriented sideways. They have a pair of prosomatic scent glands that secrete a peculiar smelling fluid when disturbed.

Harvestmen do not have silk glands and do not possess poison glands, posing absolutely no danger to humans. They do not have book lungs, and breath through trachea only. Between the base of the fourth pair of legs and the abdomen a pair of spiracles are located, one opening on each side. In more active species, spiracles are also found upon the tibia of the legs. They have a gonopore on the ventral cephalothorax, and the copulation is direct as the male has a penis (while the female has an ovipositor). All species lay eggs.

Leg oddity: The legs continue to twitch after they are detached. This is because
there are pacemakers located in the ends of the first long segment
(femur) of their legs. These pacemakers send signals via the nerves
to the muscles to extend the leg and then the leg relaxes between
signals. While some Opiliones legs will twitch for a minute, other
kinds have been recorded to twitch for up to an hour. The twitching
has been hypothesized as a means to keep the attention of a predator
while the Daddy Long Legs escapes.

Diet: Many species are omnivorous, eating primarily small insects and
all kinds of plant material and fungi; some are scavengers of the
decays of any dead animal, bird dung and other fecal material. Mating
involves direct copulation, rather than the deposition of a spermatophore.
They are mostly nocturnal and colored in hues of brown, although
there is a number of diurnal species which have vivid patterns in
yellow, green and black with varied reddish and blackish mottling
and reticulation

Myth: There is an urban legend claiming that the Daddy Long Legs is the
most venomous spider in the world, only its fangs are too small
to bite a human, and is thus not actually dangerous. This is untrue
on several counts. First, of course, they are not spiders, and none
of the known species have venom glands. The size of the jaws varies
by species, of course, but even those with relatively large jaws
are not known to bite humans (or other large creatures).

Endangered status: Some troglobitic Opiliones are considered endangered if their home caves are in or near cities where pollution and development of the land can alter the cave habitat. Others species are threatened by the invasion of non-native fire ants.

Brazil: All troglobitic species (of all animal taxa) are considered to be at least threatened in Brazil. There are four species of Opiliones in the Brazilian "National List for endangered species", all of them cave-dwelling species. Giupponia chagasi Pérez & Kury, 2002, Iandumoema uai Pinto-da-Rocha, 1996, Pachylospeleus strinatii Šilhavý, 1974 and Spaeleoleptes spaeleus H. Soares, 1966.

Argentina: Several Opiliones in Argentina appear to be "vulnerable", if not endangered. These include Pachyloidellus fulvigranulatus (Mello-Leitão, 1930), which is found only on top of Cerro Uritorco, the highest peak in the Sierras Chicas chain (provincia de Cordoba) and Pachyloides borellii (Roewer, 1925) is in rainforest patches in North West Argentina which are in an area being dramatically destroyed by humans. The cave living Picunchenops spelaeus Maury, 1988 is apparently endangered through human action. So far no harvestman has been included in any kind of a Red List in Argentina and therefore they receive no protection.